The present invention relates to improvements in the lubrication system of sealed compressors for cooling fluids.
Sealed compressors for cooling fluids are known which include a sealed casing with an alternating motor-driven compressor assembly housed in the interior thereof, the assembly including a vertical-axis crankshaft provided with a longitudinal interior lubrication duct communicating with various points on the exterior surface of the crankshaft and with an upper end of the same, eccentrically to the axis of rotation thereof. The assembly also includes a tubular device coupled to a lower end of the interior duct of the crankshaft, such tubular device having a first upper section substantially cylindrical and a second substantially conical section with an end having an orifice for the introduction of oil.
In such compressors, the oiling of the parts that are in friction is accomplished by means of the oil fluid supplied by the tubular device, which, when rotating and immersed in an oil mass, produces by centrifugal force the raising of the oil through the interior duct of the crankshaft towards the oiling points of the mechanism. Part of the oil exits out of the eccentric orifice at the upper end of the crankshaft, propelled against the interior surface of the sealed casing of the compressor.
There are various patents that disclose particular details of this oiling or lubricating system. U.S. Pat. No. 3,410,478 discloses a cylindrical tubular device joined by a conical section, as well as a wall placed in the interior of the tubular device acting as a gate, such a wall being costly to construct. U.S. Pat. No. 3,451,615 discloses a lateral outflow passage from an eccentric upper section of the interior duct of the crankshaft.
Lastly, Spanish Patent No. 504,039 discloses a channel in the extreme upper face of the crankshaft, arguing the lower cost of constructing such a channel in relation to the lateral outflow passage disclosed in the aforementioned U.S. Pat. No. 3,451,615.
It has been possible to confirm that the current solutions of tubular pumping devices lose part of their effectiveness as the compressor's operating temperature rises. Under these conditions, the fluidity of the oil mass deposited in the housing of the compressor reaches a point such that the oil mass loses velocity of rotation in relation to the velocity of rotation of the tubular device. Such device loses effectiveness as a centrifugal pump due to sliding between the interior wall of the tubular device and the layer of oil in contact with the wall.
The aforementioned interior wall that acts as a gate may, in part, solve the problem described, but it has the drawback of having a high cost of construction. Moreover, the orifice at the upper end of the crankshaft should have a certain form, so that the oil that exits therefrom has sufficient force to be propelled against the interior wall of the sealed casing of the compressor. This certain form, in the compressors that are known, entails significant difficulties in construction.